Catalyst for reducing formation of chlorinated dioxins in manufacture of chlorinated phenols

ABSTRACT

The invention covers the use of novel co-catalysts as inhibitors that reduce the formation of undesirable chlorinated dioxins during the preparation of pentachlorophenol and tetrachlorophenol from phenol or lower chlorinated phenols.

Background of the Invention

This is a division of application Ser. No. 157,447, filed June 9, 1980, now U.S. Pat. No. 4,294,996, which in turn relates to the use of novel co-catalysts which produce a reduction in the formation of undesirable chlorinated dioxin by-products in the preparation of pentachlorophenol or tetrachlorophenol from phenol or lower chlorinated phenols.

In processes well-known in the art for the chlorination of phenols or partially chlorinated phenols such as pentachlorophenol, the usual practice has been to use such catalysts as aluminum chloride, aluminum, antimony pentachloride and ferric chloride. Subsequent to chlorination, the molten tetrachlorophenol or pentachlorophenol is pumped to heated storage facilities pending flaking, prilling or molding operations which are necessary to change the material to a commercially usable form as finished product. In the case of pentachlorophenol, valuable for its fungicidal activity, the specifications are low alkali insoluble content, low insolubles in alkane solvents and a minimum of 86% pentachlorophenol content.

Prior art relating to the lowering of the amount of undesirable chlorinated dioxins formed in the preparation of pentachlorophenol is U.S. Pat. No. 4,160,114 to Shelton et al., wherein organic sulfides are directly utilized as a co-catalyst along with aluminum chloride to effect this result. The specification of the Shelton et al patent is incorporated by way of reference in this application.

There also exists prior art taught in U.S. Pat. Nos. 3,816,268 and 3,909,365 wherein chlorinated dioxins in pentachlorophenol are elaborately reduced to a lower level by distillation under vacuum using stabilizers to prevent decomposition at the required high temperatures. Although low amounts of dioxins are obtained in the distilled pentachlorophenol, a residue of pot material remains containing extremely high quantities of dioxins.

Undesirable by-products called chlorinated dioxins are present in amounts of from 200 to 8,000 parts per million in pentachlorophenol and in lesser amounts in tetrachlorophenol as manufactured by the classical phenol chlorination methods. The primary undesirable dioxins formed are hexachlorodibenzodioxins, heptachlorodibenzodioxins and octachlorodibenzodioxins.

It has been found that the amount of these chlorinated dioxins in tetrachlorophenol or pentachlorophenol can be reduced by the use of certain elements and compounds formed from these elements which, when used in conjunction with aluminum chlorination catalysts involved in synthesis, were effective in inhibiting the amount of chlorinated dioxins formed. Furthermore, these elements or compounds containing these elements acting as inhibitors for the formation of dioxins can be utilized within existing pentachlorophenol plant systems and equipment without modification or need for new construction. These inhibiting elements in low amounts can be placed within the reaction vessel along with the usual aluminum chlorination catalyst to effect reduction of chlorinated dioxins with little noticeable loss in manufacturing time and with little effort. The co-catalyst-inhibitors are also effective during holding cycles necessary in the manufacturing process. The significantly low amount of chlorinated dioxins produced during the practice of this invention exists only in the highly dispersed or diluted form in the finished product. This reduction in dioxins eliminates the necessity of disposing of highly concentrated dioxins in pot residue that arise from the distillation procedure in prior art, as well as presenting a product that has a substantially reduced dioxin content.

It has been found that certain elements have dioxin-reducing properties and can be utilized either directly in their elemental form or in halogenated or sulfonated form, or as alkyl oxides and mixtures of elements, and such compounds or elements effect the reduction of dioxins in tetrachlorophenol or pentachlorophenol produced by the standard commercial chlorination process.

Exemplary of the elements and compounds formed therefrom found to have appreciable dioxin reduction properties during the chlorination of phenols using known chlorination catalyst are antimony, bismuth, chromium, cobalt, gadolinium, germanium, iridium, magnesium, manganese, niobium, rhenium, rhodium, samarium, zirconium and tin, and the haldies, sulfides and lower alkyl oxides formed from these elements or mixtures thereof. These elements or compounds formed therefrom act as co-catalyst inhibitors with the standard known catalyst used in commercial chlorination processes to produce polychlorinated phenols by reducing significantly the formation of chlorinated dioxins which are undesirable by-products.

Typical of the catalysts used in production of chlorinated phenols and with which the co-catalyst inhibitors of this invention have been found to produce excellent chlorinated dioxin reduction results are aluminum chloride, ferric chloride, aluminum tris-butoxide, antimony chloride, stanous chloride and metallic alumina, antimony, copper, tin and mixtures thereof.

It has also been found that the presence of from about 0.0001/moles to about 0.05 moles per mole of phenol or lower chlorinated phenol of a sulfur-containing co-catalyst produces excellent results in the system using the inhibitors of this invention. Typical sulfur-bearing compounds that can be used include sulfur, diphenyl sulfide, diphenyl disulfide, dicresyl disulfide, dihexadecyl sulfide and dibenzothiophenol thiophenol, parachlorothiophenol, para, paradichlorophenyl sulfide, sodium hydrosulfide, 2,2'-thio bis (4,6-dichlorophenol) benzyl disulfide, diisopentyl sulfide, naphthalenethiol, heptyl sulfide and hexachlorophenyl sulfide.

In the manufacture of tetrachlorophenol or pentachlorophenol, the preferable quantity of the co-catalyst inhibitors to be added with the catalyst is from about 0.0001 to about 0.03 moles per mole of phenol or chlorophenol starting materials although it has been found that the use of 0.0001 to 0.5 moles of these inhibitors will produce dioxin-reducing results.

It was found that the novel co-catalyst inhibitors of this invention, when added with aluminum chloride of metallic aluminum catalysts in a phenol chlorination process, produced a pronounced reduction of chlorinated dioxins with reduction in the range of about 4% to about 26%. The following chlorinated dioxin inhibitors and mixtures thereof produced such significant reduction in total chlorinated dioxins:

Antimony pentachloride

Chromium dichloride

Chromium powder

Chromium sulfide

Cobalt metal

Gadolinium trichloride

Germanium tetrachloride

Hafnium tetrachloride

Indium chloride

Magnesium turnings

Manganese dichloride

Niobium chloride

Zirconium tetrachloride

and the following chlorinated dioxin inhibitors produced significant reduction in the more toxic hexachlorodioxins with a reduction of from about 40% to 75%:

Antimony pentachloride

Antimony powder

Bismuth trichloride

Chromium metal

Cobalt fluoride

Cobalt metal

Hafnium tetrachloride

Iridium chloride

Niobium pentachloride

Rhenium pentachloride

Rhodium chloride

Rubidium trichloride

Samarium trichloride

Tantalum chloride

Tin powder

Tungsten hexachloride

Zinc fluoride

Zirconium tetrachloride

While most of the co-catalyst-inhibitors are effective when used with an aluminum chloride catalyst, it has been found that zirconium tetrachloride and/or hafnium tetrachloride can be used as the sole catalyst with the result that chlorinated dioxins are reduced in the chlorinated phenol process.

The practice of this invention is further illustrated by the following examples. It is not intended,however, that this invention be limited by or to the examples.

Example I

A series of runs was made against controls to determine the reduction in chlorinated dioxins. The procedure for preparing pentachlorophenol from a predominatly monohlorophenol feedstock was accomplished in the following manner:

A one-kilogram sample of the feedstock plus 0.1 g of diphenylsulfide promoter were loaded into a 2,000 ml glass reactor equipped with a stirrer, heating mantle, cooling system, a thermometer, a sintered glass chlorine diffuser and an exit line for hydrochloric acid vapor. The mixture was heated to a temperature of 125° C. and chlorine gas was sparged in at 510 g/hr. During the chlorination, the chlorine feed rate was reduced stepwise to 120 g/hr so that bypassing was minimized. After two hours 0.57 g of aluminum powder or an equivalent amount of aluminum chloride was added followed by the requisite amount of the cocatalyst inhibitor. The batch temperature was held at 125° C. by water cooling until the freezing point reached 115° C.; thereafter, the batch temperature was allowed to rise so that it stayed about 10° C. above the freezing point of the reaction mixture. When the freezing point reached 178° C. to 180° C. the chlorination was stopped. Samples of the product were taken for analysis.

The results of a series of thirty runs that were made illustrate the significant reduction in undesirable dioxins obtained by the use of the inhibitors in this invention, when compared with the control runs.

In the preparation of the pentachlorophenol, various elements and halides and sulfides of the elements were used as the inhibitors, and tested against a control to determine the percent of total reduction of chlorinated dioxins. In the control runs, no co-catalyst-inhibitors were used.

The results of these tests are set forth in Table I.

EXAMPLE II

A second series of fifteen runs was made, which show the effects of varying levels of the inhibitors on reduction of chlorinated dioxin. The results of these fifteen runs are set forth in Table II which demonstrates the ranges of the amounts of inhibitors that can be used.

The following footnotes for Tables I and II show (a) the method of testing for the alkali insolubles, (b) total chlorinated phenols (TCP), and (c) the analysis of chlorinated dioxin in parts per million (PPM).

^(a) The alkali-insoluble material in pentachlorophenol is determined in the following way: Disolve a 1-gram sample in 50 milliliters of N/l NaOH and 50 milliliters of distilled water, warming to about 60° C. and crushing larger particles with flattened glass rod. Filter through a tared Gooch crucible with an asbestos mat, wash free from alkali with distilled water and dry at 100° C. to constant weight. The increase in weight represents alkali insoluble matter. It is expressed mathematically as follows: ##EQU1##

^(b) The total chlorinated phenols are determined in the following way: The total chlorinated phenol content is determined by titration of dry pentachlorophenol with sodium hydroxide.

Reagents

(a) CO₂ -free 95 percent ethyl alcohol.

Note: Ethyl alcohol denatured according to formula 2B of the appendix to Regulations No. 3, Formulae for Completely and Specially Denatured Alcohol is suitable for this purpose. Distill the ethyl alcohol (formula 2B) over caustic pellets. Store in a stoppered bottle.

(b) Meta cresol purple indicator solution. Place 0.100 grams of meta cresol purple in a small mortar, add 2.62 milliliters of N/l0 aqueous NaOH. Rub with the pestle until solution is complete. Transfer the solution to a 100-milliliter volumetric flask and make up to volume with distilled water.

Procedure

Weigh a 1.0000-gram sample and transfer to a clean 250-milliliter Erlenmeyer flask. Add 65 milliliters of ethyl alcohol and gently swirl until solution of the sample is complete. Add 35 milliliters of distilled water and subtract from above titration. Net ml. of N/lO NaOH×0.02663×100=Total chlorinated phenols as percent pentachlorophenol.

Note: Ethyl alcohol solutions pick up CO₂ from the air fairly rapidly, therefore, titrate sample immediately after dissolving in the alcohol.

^(c) All chlorodioxin analyses performed on these samples were accomplished via high pressure liquid chromatography (HPLC). Non-polar components were first isolated from the sample matrix using two passes through two alumina columns using benzene for the former and 2% methylene chloride in hexane (v/v) for the latter. The eluant was then analyzed via HPLC and quantitated for the individual chlorodibenzo-p-dioxin components.

Although the invention is described in detail for the purposes of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

    TABLE I       EFFECT OF INHIBITORS FOR REDUCTION OF CHLORINATED DIOXINS IN PENTACHLORO      PHENOL SYNTHESIS DIOXIN INHIBITOR PROPERTIES OF PCP PRODUCT    AMT.,      CAUSTIC   % REDUCTION EXPERIMENT  ATOMS OR FREEZE INSOLUBLE,.sup.a      T.C.P.,.sup.b ANALYSIS OF CHLORINATED DIOXINS, PPM.sup.c TOTAL NO. NAME      MOLES POINT, °C. % % HEXA HEPTA OCTA TOTAL DIOXINS        1 Antimony Pentachloride 0.0033 180 0.50 95.7 22 180 647 850 26.2      (SbCl.sub.5) 2 Control for Above Experiment 0.0 180 0.65 97.7 90 207 853      1150 0.0 3 Bismuth Chloride 0.0063 178 0.09 100 2.5 96.5 445.5 544.5      65.2  (BiCl.sub.3) 4 Bismuth Chloride 0.0095 178 0.30 96.8 12.6 281 804      1098 30.0  (BiCl.sub.3) 5 Bismuth Chloride and Tin 0.0063/ 178 0.05 96.2      12.6 164 811 988 36.9  (BiCl.sub.3 /Sn) 0.025 6 Bismuth Chloride and      Chromium 0.0063/ 178 0.03 97.8 10.1 138 552 700 55.3  (BiCl.sub.3 /Cr)      0.01 7 Chromium Metal 0.021 178 0.10 98.1 5.1 64 432 502 68.0  (Cr) 8      Chromium Sulfide 0.0126 178 0.33 96.7 5.1 120 638 763 51.2  (Cr.sub.2      S.sub.3) 9 Control for Above Experiments 0.0 180.5 0.20 97.6 5.1 111      1450 1566 0.0 10 Chromium Dichloride 0.0063 180.5 0.4 97.6 25 148 643      816 7.0  (CrCl.sub.2) 11 Cobalt Metal 0.017 180.5 0.23 97.5 6 91 736 832      5.1  (Co) 12 Control for Above Experiments 0.0 180.5 0.23 95.6 21 136      720 877 0.0 13 Cobalt Fluoride 0.042 179.5 0.75 94.9 24 225 756 1036 10      (CoF.sub.3) 14 Control for Above Experiment 0.0 180 0.65 97.7 90 207 853      1150 0.0 15 Gadolinium Chloride 0.0063 179 0.33 97.8 5 117.0 611.7 734      18.9  (GdCl.sub.3) 16 Control for Above Experiment 0.0 179 0.18 97.07 4      140 760 905 0.0 17 Germanium Chloride 0.0063 178 0.05 97.7 15 158 642      815 12  (GeCl.sub.4) 18 Iridium Chloride 0.0033 178 0.10 98 13 88 312      413 55.4  (IrCl.sub.3) 19 Indium Chloride 0.0063 179.5 0.03 98.5 10 82      705 797 14  (InCl) 20 Control for Above Experiment 0.0 178.5 .04 97.9 13      120 794 927 0.0 21 Magnesium Metal 0.021 180 0.30 96.7 99 181 703 984      14.5  (Mg) 22 Control for Above Experiment 0.0 180 0.65 97.7 90 207 853      1150 0.0 23 Manganese Dichloride 0.0063 181 0.20 98.3 3 41 485 529 19      (MnCl.sub.2) 24 Control for Above Experiment 0.0 179 0.18 98 4 150 809      962 0.0 25 Rhenium Pentachloride 0.0015 178 0.13 99.4 8 53 479 539 42      (ReCl.sub.5) 26 Rhodium Chloride 0.0038 178 0.08 97.7 15 117 499 631 32      (RhCl.sub.3) 27 Samarium Chloride 0.0063 180 0.48 98.4 10 76 246 332      64.2  (SmCl.sub.3) 28 Control for Above Experiments 0.0 178.5 0.035 97.9      13 120 795 927 0.0 29 Tin 0.025 178.5 0.06 97.2 8 108 585 701 42.5  (Sn)      30 Control for Above Experiment 0.0 180.5 0.20 97.6 5 111 1450 1566      0.0

                                      TABLE II                                     __________________________________________________________________________     EFFECT OF VARYING LEVELS OF INHIBITORS ON DIOXIN REDUCTION                                                                         %                          Example                                                                             Co-Catalyst     Freezing                                                                             Caustic                                                                              T.C.P.,.sup.b                                                                       Dioxins ppm.sup.c                                                                            Reduction                  No.  (atoms or moles)                                                                               Point, °C.                                                                    Insols., %.sup.a                                                                     %    Hexa                                                                              Hepta                                                                              Octa                                                                              Total                                                                              Dioxins                    __________________________________________________________________________     1    None            180   0.81  99.2 18 207 4377                                                                              4601                                                                               Control                    2    Tin Powder (0.0021)                                                                            178.5 0.83  97.0 18 249 3482                                                                              3749                                                                               18.5                       3    Tin Powder (0.21)                                                                              178   0.05  99.4 18 217  706                                                                               941                                                                               79.5                       4    Chromium Powder (0.0021)                                                                       178   0.17  97.6 18 280 1529                                                                              1827                                                                               60.3                       5    Chromium Powder (0.21)                                                                         178   0.44  99.6 107                                                                               663 3529                                                                              4299                                                                               6.6                        6    Antimony Powder (0.0021)                                                                       178   0.04  99.4 13 217 1118                                                                              1349                                                                               70.7                       7    Antimony Powder (0.21)                                                                         178   0.00  100.5                                                                               13 202 1059                                                                              1274                                                                               72.3                       8    Niobium Pentachloride (0.0021)                                                                 177.5 0.05  99.4 13 135  588                                                                               736                                                                               84.0                       9    Niobium Pentachloride (0.21)                                                                   178   1.12  98.7 72 193 1686                                                                              1951                                                                               57.6                       10   Bismuth Trichloride (0.0021)                                                                   178   0.03  98.8 18 155 1224                                                                              1397                                                                               69.6                       11   Bismuth Trichloride (0.21)                                                                     178   1.63  97.4 12 262  957                                                                              1231                                                                               73.2                       12   Manganese Dichloride (0.0021)                                                                  178   0.20  98.3 12  55  518                                                                               585                                                                               87.3                       13   Manganese Dichloride (0.21)                                                                    178.5 0.84  100.5                                                                               18 311 1565                                                                              1893                                                                               58.9                       14   Zirconium Tetrachloride (0.0021)                                                               178   0.05  98.1 15 176  790                                                                               981                                                                               78.7                       15   Zirconium Tetrachloride (0.21)                                                                 178   2.28  98.6 30 580 2761                                                                              3370                                                                               26.8                       __________________________________________________________________________ 

We claim:
 1. A catalyst used in a process of producing polychlorinated phenols having reduced amounts of chlorinated dioxin formed during the reaction of phenol or lower chlorinated phenols, or mixtures thereof, with chlorine, said catalyst selected from a group consisting of zirconium tetrachloride or hafnium tetrachloride or mixtures thereof, by reacting at a temperature of from 10° C. to 190° C. a phenol selected from the group consisting of phenols and lower chlorophenols and mixtures thereof, and chlorine to form a reaction mixture in the presence of from about 0.005 to about 0.016 moles per mole of said catalyst.
 2. The catalyst of claim 1 in which from about 0.05 to about 0.001 moles per mole of a diphenylsulfide is present in the reaction mixture. 